1. Field of the Invention
This invention relates to a method and device for controlling NOx emissions by vitiation. More particularly, this invention relates to a method and device for controlling NOx emissions by vitiation of combustion sustaining air with a controlled amount of products of combustion.
2. Description of the Prior Art
The concept of vitiation of combustion air with products of combustion to control NOx emissions is known. The products of combustion are used as a source of inert gas introduced into the air supplied for combustion to reduce or eliminate the formation of NOx. The products of combustion dilute the oxygen content, thereby lowering the concentration of oxygen in the combustion air. The resulting products of combustion/combustion air mixture reduces the flame temperature of a burner thereby controlling the evolution and, in turn, the emission of NOx.
Using this general principle, numerous attempts have been made to reduce and minimize the formation of oxides of nitrogen from the fuel and air during combustion by vitiation of combustion air with products of combustion. The present invention is a method for simply and efficiently controlling vitiation of combustion air to reduce or eliminate NOx formation. More particularly, the present invention relates to a method and device for controlling the quantity of recirculating products of combustion as a function of at least one of air preheat temperature, fuel input rate and furnace temperature to provide a reduction in NOx emissions in either a regenerative burner system, non-regenerative burner system, direct fired, or radiant tube fired system.
Accordingly, it is an object of the present invention to provide a method for reducing NOx emissions by controlling the amount of products of combustion recirculated to the furnace as a function of at least one of furnace temperature, air preheat temperature and fuel flow rate. Another object of the present invention is to provide an NOx reduction system and method for reducing NOx emissions which can be incorporated into both regenerative and non-regenerative, and both direct fired and radiant tube fired burner systems.